(1) No 1080/50p video (I suspect this has much more to do with Panasonic's processor being higher power than Sony's, rather than the sensor size difference).

(2) The RX100 has less moire (in video) than my GH3 (even when shot really flat), so is a handy alternative for some situations. (I'm pretty confident Sony are using all the pixels, Panasonic certainly aren't.)

(3) No EVF, that's the obvious step-up from the RX100.

(4) Slow GM1 mechanical shutter - but how good/bad is this? I don't know. As the flash-sync is very poor it suggests it will be bad for anything moving. (Meaning the read-out time is slow, no good having 1/16000 shutter speed if the bottom of the sensor does that 1/50 sec, or whatever, after the top.)

(5) RX100 lens is very sharp, plus fast at the wide end (even allowing for m43 sensor size it's still faster than the GM1 kit lens).

Don’t forget the RX100 only goes to 28mm eq. whereas the kit lens of the GM1 goes to 24mm eq. which is a big difference when shooting wide, especially for landscapes. Personally, if I was to choose between either faster aperture at wide-end or wider, I would choose wider, because for shooting landscapes you would generally appreciate the ability to go wider and use more DOF by stopping down to have a sharper image across the whole frame.

(6) RX100 is shirt-pocketable.

(7) RX100 AF is lightning-fast, however good the GM1 AF is it won't be usably better in real-world situations.

RX100 AF is fast-ish. I wouldn’t categorise it as ‘lighting fast’. I think both Panasonic and Olympus are slightly ahead with AF speed since they had a head start in mirrorless development (even their latest A7’s AF doesn’t feel as nippy as the latest offerings from m43). GM1’s AF is actually even faster that my EM5 which is no slouch itself.